Changing fron a 9 1/4 to 8 3/4 in my 74. Need the brake hardline for the 8 3/4. Will aCbody line work or do I use the existing line and make it work?

truck 8 3/4 housing IS the same as c-body housing 59" flange to flange so the lines should fit. vent bolt might not be same spot on tube ( or maybe I ran into that cut housings down to fit A-bodys)

I got a set of new B-body lines for 16$ off ebay. I was able to make it fit the 67 c-body housing (same as E body) buy stretching it out some to reach the wheel cyls each side.

Dr Diff can make you a new set up IIRC or he makes them long enough you can cut/flare them to fit.

Ive made so many brake lines it aint funny. Piece of cake, not something I would worry about reusing/ transferring from old rear end to new.

Or paying for a pre-bent unit.
I have to agree here.